Modified guidewire for left ventricular access lead

ABSTRACT

An improved guidewire for assisting in implantation of a cardiac lead includes three sections. The most distal zone is sufficiently floppy to prevent trauma to the vessel walls through which the guidewire and lead are inserted. An intermediate zone is generally stiffer and has a cross-section less than or equal to the cross-section of the distal zone. The third zone is stiffer yet and is joined to the intermediate zone by a shoulder. The shoulder cooperates with protrusions on the lead to transfer forces between the guidewire and lead. A finishing wire having temporary locking means to lock the finishing wire to the lead is employed to remove the guide catheter without moving the lead from its desired location. Lubricious coatings are also provided to reduce friction between the lead and guidewire.

CROSS REFERENCE TO THE RELATED APPLICATION

[0001] This patent application is a continuation-in-part of copendingapplication Ser. No. 09/164,891 filed Oct. 1, 1998, which was acontinuation-in-part of application Ser. No. 09/097,101, filed Jun. 12,1998, now abandoned.

BACKGROUND OF THE INVENTION

[0002] I. Field of the Invention

[0003] The invention relates to the implantation and placement ofcardiac leads used in combination with cardiac rhythm managementdevices, e.g., heart pacemakers or defibrillators, to monitor andcontrol the rhythm of the heart. This invention is more particularlydirected toward a guidewire/pacing lead configuration adapted to assistin the implantation and placement of a cardiac lead having one or moreelectrodes that are to reside in the distal branches of the coronaryvenous system, the great cardiac vein, or coronary sinus. The inventionalso encompasses the use of a guide catheter along with a guidewire andfinishing wire configurations useful in removing guide catheters withoutdislodging the implanted leads.

[0004] II. Discussion of the Prior Art

[0005] Placement of cardiac leads in the distal branches of the coronaryvenous system, the great cardiac vein, or the coronary sinus is adifficult task. Often when deploying the lead there comes a point atwhich the lead cannot be advanced further into the vascular system usingstandard techniques and equipment. All too often this point is not theoptimal position for the lead's electrode, either for sensing cardiacelectrical activity or delivering pacing therapy to the heart.

[0006] There are several reasons which make proper placement of the leaddifficult. These include (1) friction between the vasculature and thelead; (2) partial obstruction of the vasculature; (3) unusually shapedbifurcations in the vasculature; and (4) accumulative friction betweenlead, guide catheter and guidewire. Prior efforts to resolve suchproblems included the use of a stiffer guidewire. While stifferguidewires offer additional support, they may impede advancement due totheir relative size with respect to the lumen of the lead. Additionally,when proper placement of the lead is achieved, problems arise duringguide catheter or guidewire extraction. All too often, the act ofextracting the guide catheter and/or guidewire causes the lead to bedislodged from the implanted position. Standard guidewires and styletsare not suitable for maintaining position while the guide catheter isremoved due to insufficient stiffness, lack of appropriate forcetransmission features, and friction between the guidewire and lumen wallof the coronary vein lead. A means must be provided which will hold thelead and its corresponding electrodes in place while allowing the guidecatheter and guidewire to be removed.

[0007] The present invention is deemed to be an improvement overconventional prior art guidewires. It is more effective in properlyplacing the lead and it is also less likely to cause a properly placedlead to become dislodged during extraction of the guide catheter and theguidewire itself.

Summary of the Invention

[0008] In cases where the over-the-wire lead is to be implanted withoutthe aid of a guide catheter, the guidewire may be of a uniform stiffnessalong its length except at a distal end portion where there is attacheda floppy segment comprising a coiled wire helix having a very thin,flexible core member extending through the center of the helix and withthe distal end of the core wire affixed to an atraumatic tip. Thestiffness of the guidewire is designed to be less than the stiffness ofthe lead with which it is used. The lead is of the type having anelongated, flexible, polymeric lead body with a lumen extending the fulllength thereof from a proximal end to a distal end and of across-section allowing the guidewire to extend therethrough as the leadbody is advanced over the guidewire in placing the lead's electrode(s)at a desired location within the patient's vasculature.

[0009] Because the lead has a somewhat greater stiffness property thanits associated guidewire, there are greater frictional forces betweenthe lead and the vessel in which it is placed than between the guidewireand the wall of the lead body defining the lead's lumen. Hence, theguidewire can be removed from the lead without dragging the lead withit.

[0010] In instances where a guide catheter is first advanced through ablood vessel and into the ostium of the coronary sinus before theguidewire is inserted and the lead advanced over the guidewire, it maybecome necessary to utilize a finishing wire to hold the lead againstmovement as the surrounding guide catheter is removed subsequent toremoval of the guidewire. The finishing wire includes an element forengaging the lead and holding it stationary as the guide catheter isstripped free of the pacing lead body.

[0011] In accordance with a second embodiment of the present invention,there is provided a guidewire comprised of at least three zones. Eachzone differs from the other two in terms of its stiffness andflexibility. Each zone also has geometric characteristics which assistin proper placement of the lead and further assist in preventingdislodgement of the lead as the guide catheter is extracted and as theguidewire itself is extracted.

[0012] Specifically, the first and most distal zone is intended to bevery floppy to prevent trauma to the surrounding vessel walls when theguidewire is being advanced beyond the distal end of a guide catheterwhen deploying a coronary vein lead. This distal zone may include aspiral wound portion surrounding a thin, solid ribbon core and aspherical tip. The second zone is relatively more stiff than itsadjacent distal section and may comprise a solid wire or spiral woundwire having a cross-sectional diameter that does not exceed thecross-sectional diameter of the first zone. The second and most proximalzone is preferably of a larger diameter and is somewhat stiffer than thefirst zone but not as stiff and flexible as the lead body in which it isinserted. The second zone comprises a wire or hypo tube which can bemanipulated to apply advancement forces during deployment of the leadand stabilizing forces to a lead during extraction of the guidecatheter. A diametric transition between the first and second zones isabrupt and ideally corresponds to a matching feature in the lead so thatthis transition is the point where most of the advancement forces andcounter forces are transmitted to the lead.

[0013] In a third embodiment, a finishing wire is provided which has asquared end for engaging a portion of the lead to hold it in placeduring guide catheter removal. The guide catheter easily disengages fromthe lead for withdrawal of the finishing wire.

[0014] In yet another embodiment a three zone finishing wire is usedwhich extends beyond the length of the guide catheter, but does not exitthe lead to frictionally hold the lead in place while removing the guidecatheter.

[0015] In still another embodiment the three zone finishing wire isprovided with a temporary locking means to hold the lead in place whileremoving the guide catheter. The temporary locking means can beproximal, distal or both. The temporary locking means can also be alongthe length of the finishing wire or in the lumen of the lead.

[0016] In a further embodiment the finishing wire with the temporarylocking means can be modified to have only one zone.

[0017] Other improvements also exist. For example, the improvedguidewire (or portions thereof) can be provided with a hydrophiliccoating to produce a highly lubricious surface. The presence of such asurface reduces friction between the lumen wall of the lead and theguidewire thereby reducing the risk that the lead will be dislodgedduring extraction of the guidewire.

DESCRIPTION OF THE DRAWINGS

[0018] The foregoing features, objects and advantages of the presentinvention will become more clear to those skilled in the art from thefollowing detailed description of a preferred embodiment, particularlywhen considered in conjunction with the accompanying drawings in whichlike numerals in the several views refer to corresponding parts.

[0019]FIG. 1 is a view showing an intravenous cardiac lead having anelectrode positioned in a coronary vein, a segment of a guide catheter,a finishing wire and a proximal end locking means;

[0020]FIG. 1A is a fragmentary view showing an alternative lockingmechanism;

[0021]FIG. 1B is a fragmentary view showing a further alternativelocking mechanism;

[0022]FIG. 2 is a perspective view of a preferred embodiment of aguidewire of the present invention;

[0023]FIG. 3 is a cross-sectional view of a cardiac lead with aguidewire pf FIG. 2 positioned within the lumen of the lead;

[0024]FIG. 4 is a plan view of an embodiment of a finishing wire made inaccordance with the present invention;

[0025]FIG. 5 is a cross-sectional view of a cardiac lead surrounded by aguide catheter and with a finishing wire of the type shown in FIG. 4positioned within the lumen of the lead;

[0026]FIG. 6 is a cross-section of the distal zone of the guidewireshown in FIG. 1;

[0027]FIG. 7 is a cross-section of a guide catheter, lead and finishingwire with a spherical tip and a temporary locking mechanism in theproximal zone;

[0028]FIG. 8 is a fragmentary side view of a finishing wire with abullet tip and a temporary locking mechanism in the intermediate zone;

[0029]FIG. 9 is a fragmentary side view of a finishing wire with atapered tip and a temporary locking mechanism in the distal zone; and

[0030]FIG. 10 is a partial side view of a finishing wire having aproximal zone and a distal zone with a bullet tip and an expandableelement as a temporary locking mechanism on a large portion of thelength of the proximal zone of the finishing wire.

DETAILED DESCRIPTION OF THE INVENTION

[0031]FIG. 1 shows a human heart 1 with a coronary lead 10 passingthrough the superior vena cava 2, the right atrium 3, and the coronarysinus 4 into the great vein 5 of the heart 1 so that an electrode 12 onthe lead 10 is properly positioned in a branch of the coronary vein onthe left sides of the heart. When positioned as shown, the electrode 12can be used to either sense the electrical activity of the heart or toapply stimulating pulses to the left ventricle 7 without the electrodebeing positioned within the left ventricular chamber. A portion of aguide catheter 8 is used to insert the lead into the heart 1. Thepresent invention is concerned with guidewires and/or finishing wiresuseful for placing leads 10 and their electrodes in the vasculature andfor removing the associated guide catheter 8 and a guidewire 20 withoutdislodging the leads 10 and its electrode(s) 12. As used herein, theterm “guidewires” includes both the guidewires used to install the leadsand “finishing wires” also known as “removal wires” used for removingthe guide catheter without moving the leads. In some embodimentsdisclosed herein the guidewires also function as finishing wires and inothers, a separate guidewire and finishing wire is employed.

[0032]FIG. 2 shows a first preferred embodiment of a guidewire 20advantageously used to position the coronary lead 10 as shown in FIG. 1and retain the coronary lead in that position as the guide catheter 8 isremoved. Guidewire 20 in FIG. 2 has three zones, a distal zone 22,intermediate zone 24, and a proximal zone 26. As will be laterdescribed, a two zone guidewire can also be employed in the practice ofthe invention.

[0033] With continued reference to FIG. 2, the distal zone 22, as bestseen in FIG. 6, preferably may be about 1 to 1.5 inches long. The distalzone 22 is circular in cross-section and may have a cross-sectionaldiameter of approximately 0.014 inches. The distal zone 22 comprises aninternal shapeable ribbon core member 28 (FIG. 6), a spiral winding 30and a spherical tip 32. The internal ribbon core member 28, as itextends distally, may taper from about 0.005 inches to about 0.001inches. This construction is sufficiently floppy such that there is notrauma induced by the guidewire to a surrounding vessel wall as theguidewire is advanced through the vasculature. This construction alsoallows it to be capable of being biased so as to aid in steering throughthe vasculature.

[0034] The intermediate zone 24 is generally slightly stiffer than thedistal zone 22. The intermediate zone may comprise a solid wire having acircular cross-section. The cross-sectional diameter of the wire canvary depending upon the performance needs, but should not exceed thecross-sectional diameter of distal zone 22. The length of intermediatezone 24 can also vary, but preferably will be one to four inches long.

[0035] The proximal zone 26 is made of a wire or tubing and is thestiffest and longest section of the guidewire 20. The proximal zone 26,being the stiffest and most proximal, is the portion handled and used bythe medical professional to apply forces during deployment and guidecatheter extraction. Preferably, the overall length of the guidewire 20will be in the range of four to five feet. The cross-sectional diameterof the proximal zone 26 is larger than the cross-sectional diameter ofthe distal zone 22 and the intermediate zone 24. For example, if thedistal and intermediate zones have a diameter of approximately 0.014inches, the proximal zone could have a diameter of approximately 0.022inches. The diametrical transition between the proximal and intermediatezones taper, though abruptly, from about 0.022 inches to about 0.014inches. As discussed below, this diametrical transition constitutes ashoulder 34 through which most of the advancement and stabilizing forcesare transmitted between the lead 10 and guidewire 20 during insertion ofthe guidewire 10 and extraction of the guide catheter 8. The dimensionsset out herein are intended to be illustrative, but not limitive.

[0036]FIG. 3 shows the guidewire 20 of FIG. 2 positioned within a lumen14 of the coronary lead 10. The lumen 14 preferably has a transition 16which corresponds to the shoulder 34 of the guidewire 20. When theshoulder 34 engages the transition 16, advancement forces applied to theguidewire 20 during insertion of the guidewire 20 are transferred to thelead 10 through the shoulder 34 and transition 16 which is a reductionin lumen diameter. Similarly when the guide catheter 8, FIG. 1, isextracted from the lead 20, transition 16 is held in place by shoulder34 the guidewire 20.

[0037]FIGS. 4 and 5 show another embodiment of a guidewire 120. Thistype of guidewire 120 is referred to herein as a removal wire orfinishing wire. It is ideally suited for use during removal of a guidecatheter 8to prevent lead displacement. After a guidewire is used toinsert the lead, the guidewire is first withdrawn and replaced by afinishing wire 120 that is inserted to retain the lead 10 in placeduring extraction of the surrounding guide catheter 8. Again, thefinishing wire 120 of this embodiment may comprise three zones—a distalzone 122, an intermediate zone 124, and a proximal zone 126. Thefinishing wire 120 shown in FIGS. 4 and 5 is dimensioned somewhat in afashion similar to the guidewire shown in FIGS. 2 and 3. The primarydifference between the finishing wire shown in FIGS. 4 and 5 and theguidewire shown in FIGS. 2 and 3 is that the distal tip 132 in FIGS. 4and 5 are not attached to the core 128 by a solder joint. Also, thedistal tip 132 of this embodiment is not intended to exit the distal endof the lead 10, thus it is not shapeable or steerable in the vasculaturenor is an atraumatic spherical tip required. Finishing wire 120 may beused to lock into the lead 10 and transmit force to the lead tip, but isonly used in conjunction with the lead 10 during removal of the guidecatheter 8. The spiral wound wire in the intermediate zone 124 may besecured to the proximal zone 126 by a solder joint or by crimping. Thedirection of the winding 124 will preferably be opposite that of anywinding 11 of the elongated conductor of lead 10 itself. This allows forbetter tracking through the central lumen 14 of the lead 10. The distalzone 122 is a continuation of the spiral winding of the intermediatezone 124. However, the diameter of the winding increases to form thedistal zone 122. The distal tip 132 of the coil which forms theintermediate end distal zones is cut square and not attached to a corewire or the like. Thus, as the guide catheter 8 is withdrawn, the squarecut of tip 132 seats in the taper of the coil 11 of the lead 10preventing the lead from withdrawing as the guide catheter 8 is pulledfree. Furthermore, as the finishing wire 20 is pulled free from the lead10, the square, unattached coil tip 132 slightly distends and easilyfrees itself from the tapered coil section 11 of the lead 10. Thisfeature allows for easy, predictable removal of the finishing wire 120from the lead 10, thus preventing loss of purchase of the lead upon itswithdrawal.

[0038] In other embodiments, a finishing wire 220, 320 and 420, as shownin FIGS. 7, 8, and 9, respectively, may be used to extract the guidecatheter 8 while leaving the lead 10 and its electrodes in place. Asshown in FIG. 7, the finishing wire 220 is inserted into the lead 10 andextends some distance past the distal end of the guide catheter 8, butshort of the end of the lead 10. Although FIG. 7 is shown with thecatheter guide 8, lead 10 and finishing wire 220 in a concentric,collinear relation, when, inside of the heart, they really have a curvedtortuous path. The catheter guide 8, lead 10 and finishing wire 220 willbe in frictional contact with each other over a curved path. The lead 10will be in frictional contact with the guide catheter 8 making itdifficult to withdraw the guide catheter 8 without applying a force tothe lead 10 that tends to withdraw the lead. It is desired to leave thelead in its originally placed position to maintain the optimal placementof the electrodes. The finishing wire 220 is used to maintain the lead10 in place while withdrawing the guide catheter 8. Since the finishingwire 220 extends beyond the length of the guiding catheter 8 the totalfrictional contact area between the finishing wire 220 and the lead 10will be greater than the frictional contact area between the guidecatheter 8 and the lead 10, thus the lead 10 will tend to stay in placeas the guide catheter 8 is withdrawn, particularly if the finishing wire220 extends substantially past the end of the guide catheter 8 and ismaintained stationary. Following removal of the guide catheter, thefinishing wire can be removed by extracting it from the lumen 14 of thelead 10 by simply pulling it out while holding the proximal end of thelead to prevent it from being dislodged from the position it had beenplaced in.

[0039] As shown in FIG. 7 the finishing wire 220 has a spherical tip 50for ease of inserting and withdrawing the finishing wire 220 over thelength of lead 10. FIG. 8 shows a finishing wire 320 having a bulletshaped tip 51 for ease of inserting and withdrawing the finishing wire320 in the lead 10. FIG. 9 shows another embodiment of the finishingwire 420 with a tapered tip 52. The tips 50, 51 and 52 on the finishingwires 220, 320 and 420 should be atraumatic tips to avoid punctures ofthe leads 10 and the veins in case the finishing wire is allowed to exitthe distal end of lead 10.

[0040] In other embodiments the spherical tip 50, the bullet tip 51 andthe tapered tip 52 may be made to frictionally contact lead 10 to helphold the lead in place.

[0041] In the embodiments of FIGS. 7, 8 and 9 the finishing wires 220,320, and 420 may have additional means 60 for temporarily locking to thelead 10 at the distal end of the lead 10 such that the guide catheter 8can be removed without the lead 10 being dislodged. Any number of meansfor temporarily locking the lead 10 at the distal end of the finishingwire may be employed. For example, in U.S. Pat. No. 5,011,482 to Goodeet al., FIGS. 10 to 19 disclose expandable balloons, and radiallyexpanding projections, such as deformable strips, radially expandingbarbs, expanding sleeves, and off center (eccentric) cylinders on thefinishing wire for temporarily locking the finishing wire onto the leadand holding the lead in place while a guide catheter is removed. InGoode et al U.S. Pat. No. 5,013,310 a wire is radially unwound forengaging the lead and locking the lead in place. In Pearson et al. U.S.Pat. No. 5,769,858 the distal end of the finishing wire is bent into aJ-shape hook at the distal end for engaging the lead and holding it inplace while the guide catheter is removed. These patents show somemeans, but not the only means, for temporarily locking the distal end ofthe finishing wire to the lead. U.S. Pat. Nos. 5,769,858, 5,013,310 and5,011,482 are hereby incorporated herein by reference.

[0042] Alternatively, the finishing wires 20, 120, 220, 320, and 420 inthe several embodiments may have a means of temporarily locking to thelead 10 at the proximal end of the lead, as at locking connection 80shown in FIG. 1 abutting the proximal end of the terminal pin 70, suchthat the lead 10 will be held in place while the guide catheter 8 isremoved by slipping it back over the locking connection 80. In anotherembodiment shown in FIG. 1A, the locking connection 80′ comprises asuture 81 where the suture affixed to the finishing wire 20 is made toabut the proximal end of the leads terminal pin 70 to hold the lead inplace as the guide catheter 8 is removed. In another embodiment, thelocking connection 80 can be achieved by slipping a short length of hypotubing over the finishing wire and bonding or welding the two together,such that he distal end of the hypo tube 80′ creates a shoulder thatabuts the free end of terminal pin 70. See FIG. 1B. In still otherembodiments the terminal pin 70 may have a collet or other temporarylocking device for engaging and holding the lead 10 in place on thefinishing wire. The locking element must be sufficiently small in sizeto allow the guide catheter to strip over it. In some embodiments, boththe distal temporary locking mechanism 60 and the proximal temporarylocking mechanism 80 can be used simultaneously.

[0043] Although the finishing wires 20, 120, 220, 320 and 420 shown inthe various figures may be of the three-zone design, they need notnecessarily have a distal zone 22 which is designed to be very flexiblesince the finishing wire need not exit the distal end of the lead.Similarly the finishing wires may not need an intermediate zone 24 sincethe flexibility inside of the lead is not as much of an issue as whenthe guidewire and the lead were in the vein without a guide catheter.However, the finishing wires have to be flexible enough to snake theirway through the lead 10 without damaging the lead or exiting the leadand damaging the vein in which the lead is located. The finishing wiremay have one continuous zone for this purpose. The distal tips may be ofthe spherical, bullet or tapered designs. Such finishing wires may havejust a single zone, or both a proximal zone and a flexible distal zone,or a proximal zone, an intermediate zone, and a flexible distal zone.

[0044] For finishing wires 20, 120, 220, 320, 420 with a distal zone 22,a intermediate zone 24 and a proximal zone 26 a temporary locking means60 is preferably used in the proximal zone 26 for greatest lockingstability and stiffness. However the temporary locking means 60 may bein the distal zone 22 or the intermediate zone 24.

[0045] In another embodiment shown in FIG. 10, the entire length or apredetermined portion of the finishing wire 20 within the lead can beexpanded, such as with a braided element 90, to temporarily lock thefinishing wire 20 securely to the lead. The element 90 acts likeso-called “Chinese handcuffs”. It expands by contracting the braidedwire mesh material along its length by moving the edge 95 thereof indirection 97. The radius of the braided element thereby increases toprovide a large surface contact area and, thus, firm grip on the lead10. The braided element 90 is radially retracted by pulling the braidedelement at the edge of the element 95 in direction 96. In this mannerthe finishing wire is unlocked from the lead. A braided element 90 maybe of a shorter length and be used as the temporary locking means 60 inthe embodiments of FIGS. 7, 8, and 9.

[0046] In all of the embodiments, a hydrophilic coating can be appliedto create a surface 21 (FIG. 3) on the guidewire 20 that is highlylubricious. Alternatively, all surfaces of guidewire 20 can be coatedwith a hydrophilic coating, of polytetrafluoroethylene (PTFE), or someother dry lubricious material, i.e. silicone film. This serves to reducefriction between the guidewire 20 and lead lumen 14 of the lead therebyreducing the risk that the lead 10 will be dislodged from its properposition as the guidewire 20 is extracted.

What is claimed is:
 1. Apparatus for facilitating placement of a cardiacpacing lead within the vascular system of a patient comprising: (a) anelongated guidewire of a first predetermined flexibility and having apredetermined outer diameter and length; (b) an elongated, polymericlead body whose flexibility is less than the predetermined flexibilityof the guidewire, the lead body having a proximal end, a distal end anda lumen extending therebetween, said lumen sized to receive theguidewire therethrough and with an electrode disposed on the lead bodyproximate the distal end thereof; and (c) means on the guidewire adaptedto cooperate with a predetermined portion of the lead body when theproximal end of the guidewire is pushed in a distal direction forpositioning the electrode at a desired location in the vascular system,the flexibility of the guidewire relative to the lead body maintainingthe electrode at the desired location as the guidewire is extracted fromthe lumen.
 2. The apparatus of claim 1 wherein the guidewire comprises:a. a floppy distal zone having a spiral winding; b. a contiguous zonejoined to said floppy distal zone, the largest cross-sectional diameterof said contiguous zone being no larger than the largest cross-sectionaldiameter of said floppy distal zone and exhibiting said firstpredetermined flexibility.
 3. The apparatus of claim 2 wherein saidcontiguous zone is made of a material which makes said contiguous zonestiffer than said floppy distal zone.
 4. The apparatus of claim 2wherein said contiguous zone comprises a solid wire.
 5. The apparatus ofclaim 4 wherein said solid wire has a circular cross-section.
 6. Theapparatus of claim 1 wherein at least a portion of said guidewire has alubricious outer surface.
 7. The apparatus of claim 6 wherein saidlubricious outer surface is a hydrophilic coating.
 8. The apparatus ofclaim 6 wherein said lubricious outer surface comprises apolytetrafluoroethylene coating.
 9. The apparatus of claim 6 whereinsaid lubricious outer surface comprises a silicone film coating.
 10. Forimplantation and placement of at least one cardiac electrode, anapparatus comprising: (a) a cardiac lead having said electrode disposedthereon, the lead having a lumen defined by a wall and a transitiondefining a shoulder projecting inwardly from said wall; (b) a guidewireadapted to fit through said lumen and comprising: (1) a floppy distalzone with a spiral winding; (2) a contiguous proximal zone joined tosaid floppy distal zone, said proximal zone comprising a solid wirehaving a shoulder dimensioned to engage the shoulder projecting inwardlyfrom the lumen wall of the cardiac lead when said guidewire is insertedinto said lumen, said proximal zone being stiffer than the floppy distalzone.
 11. The apparatus of claim 10 and further including anintermediate zone, comprises a spiral wound wire.
 12. The apparatus ofclaim 10 and further including an intermediate zone between the proximalzone and the distal zone which comprises a solid wire having a circularcross-section.
 13. The apparatus of claim 10 further comprising meansfor temporarily locking said guidewire to said lead.
 14. Forimplantation and placement of at least one cardiac electrode, anapparatus comprising: (a) a cardiac lead having said electrode disposedthereon and having an interior wall defining a lumen; (b) a guidewirecomprising: (i) a floppy distal zone comprising a spiral windingsurrounding a ribbon core member, and a spherical tip covering one endof the ribbon core member and the spiral winding; (ii) an intermediatezone joined to said floppy distal zone; and (iii) a proximal zone joinedto said intermediate zone, said proximal zone being stiffer than boththe floppy distal zone and the intermediate zone. (c) means fortransmitting forces between said cardiac lead and said guidewire. 15.The apparatus of claim 13 wherein said means for transmitting forcesbetween said cardiac lead and said guidewire includes a shoulder formedbetween the proximal zone and intermediate zone of the guidewire forengaging a member projecting from the interior wall of the lumen of thecardiac lead.
 16. For use in combination with a guide catheter toimplant a cardiac lead, said cardiac lead having at least one electrode,a central lumen defined by a helically wound wire coil turned in a firstdirection, a guidewire comprising: (a) a distal zone comprising a spiralwinding turned in a second direction opposite to the first direction andhaving a square cut tip; (b) an intermediate zone joined to said distalzone, the largest cross-sectional diameter of said intermediate zonebeing no larger than the largest cross-sectional diameter of said distalzone; and (c) a proximal zone having a cross-sectional diameter greaterthan the largest cross-sectional diameter of said intermediate zone,said proximal zone being joined to said intermediate zone by a taperedshoulder and being stiffer than both the distal zone and theintermediate zone.
 17. The apparatus of claim 16 wherein said guidewirehas a diameter sufficiently small to be insertable into said centrallumen after placement of the lead yet the distal zone has a diametersufficiently large that said tip is able engage the wire coil whichdefines said lumen to retain the lead in place during removal of theguide catheter.
 18. In combination with a guide catheter and a cardiacstimulating lead, a finishing wire for insertion in the lumen of thecardiac lead for removing said guide catheter while holding the lead inplace, comprising: a floppy distal zone with a distal tip, anintermediate zone joined to said floppy zone, the intermediate zonehaving a stiffness different from that of the floppy distal zone, and aproximal zone joined to the intermediate zone, the proximal zone beingstiffer than the intermediate zone and the floppy zone wherein thefinishing wire, when inserted past the distal end of the guide catheter,engages fictionally and holds the lead in place during removal of theguide catheter.
 19. A finishing wire as in claim 18 wherein, the distaltip has an atraumatic spherical tip. e distal tip has an atraumatictapered tip.
 20. A finishing wire as in claim 18 and further including ameans for temporarily locking the finishing wire to the lead duringremoval for the guide catheter.
 21. A finishing wire as in claim 20wherein, the means for temporarily locking is attached to the distal endof the finishing wire.
 22. A finishing wire as in claim 18 wherein, themeans for temporarily locking is attached proximate to the proximal endof the finishing wire.
 23. A finishing wire as in claim 18 wherein, themeans for temporarily locking is attached to the finishing wireproximate the proximal end thereof and a separate temporary lockingmeans is disposed proximate the distal end of the finishing wire.
 24. Afinishing wire as in claim 18 wherein, the temporary locking meansextends along a predetermined length of the finishing wire.
 25. Afinishing wire as in claim 22 wherein, the temporary locking meanscomprises a radially expandable and contractible braided elementattached to the finishing wire.
 26. A finishing wire as in claim 20wherein, the temporary locking means comprises sutures on the finishingwire adapted to cooperate with a terminal pin on the cardiac lead.
 27. Afinishing wire as in claim 16 and further including, a means fortemporarily locking the finishing wire to the lead during removal forthe guide catheter.
 28. A finishing wire as in claim 27 wherein, themeans for temporarily locking is attached proximate to the distal end ofthe finishing wire.
 29. A finishing wire as in claim 27 wherein, themeans for temporarily locking is attached proximate to the proximal endof the finishing wire.
 30. A finishing wire as in claim 27 wherein, thetemporary locking means extends along a predetermined length of thefinishing wire.
 31. A finishing wire as in claim 30 wherein, thetemporary locking means comprises a radially expandable and contractiblebraided element attached to the finishing wire.
 32. A finishing wire asin claim 27 wherein, the temporary locking means comprises suturescooperating with a terminal pin on the lead.
 33. A finishing wire as inclaim 29 wherein, the temporary locking means comprises a shoulder onthe lead for engaging a shoulder on the finishing wire.
 34. A method forinstalling a pacing lead within a patient comprising the steps of:providing a guide catheter, a body implantable pacing lead and anelongated finishing wire; advancing the guide catheter through thevascular system of a patient until a distal end thereof is at apredetermined location; advancing the pacing lead through the guidecatheter until an electrode on a distal end portion of the pacing leadis positioned beyond a distal end of the guide catheter and adjacenttissue to be stimulated; inserting a finishing wire into a lumen of thepacing lead, the finishing wire engaging a wall defining the lumen ofthe lead to permit the guide catheter to be removed from surroundingrelation with the lead without the lead being moved from a desiredplacement; removing the guide catheter from the patient; and removingthe finishing wire from the lumen of the lead while holding the proximalend of the lead so that the lead is not dislodged during removal of thefinishing wire from the patient.
 35. The method of claim 34 and furthercomprising the step of: temporarily locking the finishing wire to thelead at the distal end of the finishing wire while the guide catheter isbeing removed.
 36. A method of removing a guide catheter fromsurrounding relation with respect to an over-the-wire pacing lead havingan electrode thereon proximate a distal end thereof after the pacinglead has been installed in a patient with the electrode at a desiredlocation, comprising the step of: (a) removing a guidewire from a lumenof the over-the-wire pacing lead; (b) inserting a finishing wire intothe lumen of the over-the-wire pacing lead, said finishing wire having ameans for engaging the finishing wire with the lead; (c) stripping theguide catheter from the over-the-wire pacing lead and over a proximalportion of the finishing wire while holding the finishing wirestationary; and (d) withdrawing the finishing wire from the patientwhile holding a proximal end of the pacing lead stationary so as not todisplace the electrode from the desired location.
 37. A method forinstalling a cardiac pacing lead in a patient, comprising the steps of:(a) providing a pacing lead having an elongated flexible tubular bodywith a proximal end, a distal end and a lumen extending therebetween,the lead body supporting an electrode proximate the distal end; (b)providing a guiding catheter having an elongated flexible tubular bodywith a proximal end, a distal end and a lumen extending therebetween,the lumen of the guiding catheter sized to permit passage of the pacinglead therethrough; (c) providing an elongated flexible guidewire havingan atraumatic distal tip, the guidewire having an outer diameter of asize permitting passage thereof through the lumen of the pacing lead;(d) providing an elongated flexible finishing wire having an outerdiameter smaller than a diameter of the lumen of the pacing lead; (e)percutaneously inserting the distal end of the guiding catheter into thevascular system at a predetermined location and advancing the guidingcatheter along the vascular system until the distal end of the guidingcatheter reaches a predetermined location; (f) advancing the guidewirethrough the lumen of the guiding catheter with the distal tip of theguidewire extending beyond the distal end of the guiding catheter to atarget location where the electrode on the pacing lead is to bepositioned in the patient; (g) threading the distal end of the pacinglead onto the proximal end of the guidewire and advancing the pacinglead over the guidewire until the electrode is at the target location;(h) holding the proximal end portion of the pacing lead whilewithdrawing the guidewire from the lumen of the pacing lead; (i)inserting the finishing wire at least partially within the lumen of thepacing lead; (j) holding the proximal end portion of the finishing wireto stabilize the pacing lead against movement while removing the guidingcatheter from the patient; and (k) removing the finishing wire from thelumen of the pacing lead and from the patient.